Looks like it's going to be Mercedes-powered teams vs. everyone else.

Blogf1.it reports that the Frenchman missed the first week of testing in Bahrain, where Renault's V6 'power unit' crisis continued to unfurl, because he had to have his appendix removed.

The report said Taffin is now recovering.

It is an awkward time for Renault Sport, mere days before performance development of its troubled 2014 'power unit' is mandatorily frozen by the FIA.

Clearly, the Mercedes-powered teams Mercedes, McLaren, Williams and Force India - in roughly that order - are leading the pack.

"It would be engine dominated this year," said Force India's deputy boss Bob Fernley, "and the biggest differential for teams would be who got the right engine and at the right time."

It is said Ferrari is next best, but Germany's Auto Motor und Sport repeated paddock rumours that the Italian marque is taking a very cautious approach to the revolutionary new era and could have plenty of performance still up its sleeve.

France's L'Equipe quotes Ferrari driver Kimi Raikkonen as admitting: "Our laptimes are so far not very impressive, but we will see where we really are in Australia.

"On reliability, everything is fine, but on performance, we don't know too much, although I don't think it's bad," said the Finn.

Force India's Fernley added: "It looks at the moment that Mercedes have a slight lead," he told Britain's Sky, "but that will change -- it's only a matter of time."

For Renault, however, it could be a matter of a substantial amount of time, with world champion Red Bull's Dr Helmut Marko admitting the current situation is "not pleasing".

"It is not Renault('s fault) exclusively, but the main problems are with Renault," he told Kleine Zeitung newspaper.

"And it applies not only to Red Bull, but to all the Renault teams."

When asked for details of the problems, Marko answered: "It's a collection of things with such complexity that cannot be explained in two sentences."

Auto Motor und Sport claims the current laptime gap between Mercedes and McLaren, the leading Mercedes-powered teams, is nine tenths.

But Mercedes team chairman Niki Lauda suggested the Brackley team might simply be having a smoother time in the winter amid the sport's radical transition phase.

"We probably have the same problems as the others," he said, "only less of it."